I honestly don't know what an alien should look like. In my estimation, an alien who could travel to Earth would be smarter, more evolved than we are, and as such, their species would reflect that, which is to say: They've already invented fat-busting pills, a cure for baldness, and they're all a genetically engineered, super-hot species. They shouldn't be ugly, green creatures. They should look better than us. They shouldn't look like they're from Mars; they should look like they're from Hollywood.